Copper-extbactioh psocess



www @am 18 1927' w. E. GREENAWALT COPPER EXTRACTION PROCESS Filed` June8. 1926 Ore O" Concentraior Hi h Grade Low Grade CoglcentrateConeentrate Roastmg .-,J H.G.Cor|.Rea1 ue Furnace la'lcilllrrk.

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. 1 COPP'I' 50] Cuz +Cuf 5 @5b Aglterkof 7 eparaj r HGCCm'NO Seitler No1leq(l v Elec.Umt No 1 Copper '12am-ks Aglfa r N settler 'L ElecUmt No 2Copp er Tmks Aglao N 5 Setder o5 Hugh Grade Eiec-umt No5 Concentrate 4Residue Coppe]- Tanks Reg enexted Aad Solution r Foul or Ex cess Acld.Solwntin IMNT'OR Patented dan. 18, i927.

COPPER-EXTRACTON PROCESS.

Application filed June 8,

rlhe process has as its object the production ot electrolytic copperfrom its ores Without resorting to regular smelting and refiningmethods, which, in most mining districts, are too expensive for generaladoption.

The following considerations are the principal tactors governing theprocess, and When these are understood the process can be easilycomprehended.

In leaching copper ore With an acid solution, such as sulphuric acid,iron is always dissolved With the copper. In the electrolysis of coppersolutions containing salts of iron, copper is deposited While sulphuricacid and ferrie iron are regenerated, as shown by the followingequation:

CuSO4-lf2l5`eSOA-electrolysis:

CIH-QHaSOi-l-l/Fez i S04) ai in Which m represents an indeterminateamount of sulphuric acid and g/ an indeterminate amount of ferriesulphate. `The relative amounts of acid and erric sulphate produced bythe electrolysis Will largely depend on the details of operation, suchas the iron content o the electrolyte, the temperature of theelectrolyte, and the composition of the anodes. Lead anodes, torexample, will usually give a relatively large amount oli sulphuric acidwith a relatively small amount ot ferrie sulphate, While carbon anodesWill usually give a relatively large amount ot Jferrie sulphate with arelatively .small amount of sulphuric acid.

Ferrie sulphate in the electrolyte is harmtul; it re-dissolves coppersomewhat in proportion to its presence in the electrolyte. Ferroussulphate is quite harmless, and it may be beneiicial. The crucialproblem of the deposition ot copper from solutions containing salts ofiron, practically resolves itself to the control, or reduction, or" the'ferrie iron produced in the deposition yof the copper. There are anumber of practical reducing agents available for this purpose, amongwhich may be mentioned, sulphur dioxide, metallic copper, and coppersulphide. ylhe present process is directed more particularly to aspecific and economical application of copper sulphide, as related tothe general treatment ot the ore.

rlhe reduction of erric iron becomes more difficult as the solutionincreases in acidity. Ferrie sulphate is easily reduced in neutral 1926.Serial No. 114,477.

or slightly acid solutions, While its effective reduction in highly acidsolutions is Very diiticult. For this reason the solution should notcontain an excessive amo-unt ot acid unless a large amount ot acid isdesired for other purposes. v

Sulphur dioxide is an eiiective reducing agent 'for ferrie iron undersome conditions it properly applied, as for example, as set torch in mypatents No. 1,353,995, Sept. 28, 1920, and No. 1,483,056, Feb. 5, 1924.If terric sulphate is reduced with sulphur dioxide a large amount ofacid is regenerated, as shown by the equation,

Frequently such a regeneration ot acid is desirable for leachingpurposes, but it also frequently happens that it may be objectionable,especially in the treatment ot high grade ore or concentrate Where theacid consumption is relatively small.

lt the ferrie iron is reduced with copper sulphide, as set forth in somedetail in my patents, No. 1,340,826, May 18, 1920 No. 1,357,495, Nov. 2,1920, and No. 1,489,121, Apr. 1, 1924, copper goes into solution withthe simultaneous reduction of the terric iron, While little or no acidis regenerated, as shown by the equations:

The copper sulphide may be either the natural sulphide, such aschalcocite, corellite, or chalcopyrite; a high grade copper matte asobtained 'from smelting; or a, precipitate obtained by precipitatingcopper from lean and foul solutions with a sulphide precipitant .such ashydrogen sulphide.

rlhe applica-tion of sulphur dioxide tothe leach solution, orelectrolyte, is usually advantageous, but it will be seen that it theelectrolysis is conducted in such a Way as to generate. a maximum amountot' terric iron and a minimum amount of acid, and the ferrie iron isreduced with copper sulphide, a considerable savingy would result overother methods of procedure, for the reason that copper Would go intosolution at the expense `of the ferrie iron and would be deposited asthe electrolytic metal, While the acidity of the solution could be keptunder control. A Wide range of operating lili) conditions could thus bemaintained by increasing or diminishing the variable factors of theprocess.

Carbon anodes, if they can be used, would regenerate a maximum' amountof ferrie iron and a minimum amount of acid. If carbon anodes are usedit is desirable to have a warm or hot electrolyte and vigorouscirculation or agitation to facilitate depolarization, which appears tobe essential for the preservation of carbon anodes and the generation oflarge quantities of ferrie iron in the deposition of copper from coppersolutions containing salts of iron. But whether carbon, lead, or otheranodes are used, it is desirable to maintain the temperature of thesolution fairly warm, because both the deposition of the copper and thereduction of the ferrie iron with copper sulphide are better with hot orwarm solutions than with cold solutions.

Fei-ric sulphate is a solvent for copper in its sulphide combinations,while sulphuric acid is not. It might be said that the hotterthesolution of ferrie sulphate the more effective it is as a solvent forcopper in its sulphide combinations, and the more effective ferroussulphate is as a depolarizer in Vthe deposition of the copper. Hetsolutions are not always desirable, but under the conditions of thisprocess hot solutions can he economically maintained and present certainadvantages.

As another condition entering into the process in the treatment ofsulphide concentrates, for example, roasting is an important matter.Under certain conditions of roasting it has been found that from to ormore, of the copper can be made soluble in water by roasting, and that avery high total extraction of the copper is possible with such a roast.But, with a large percentage of water soluble copper due to roasting,the amount of acid regenerated in the deposition of the copper should bemaintained low for the most satisfactory operation. The excess acid tobe wasted should be maintained as low as possible, unless oxidized oreis available for its use and neutralization, and oxidized ore is notalways available in the treatment of sulphide concentrates.

As a result of these considerations and conditions, it has been foundthat a simple and effective process can be applied to the treatment ofmany or most copper ores, in

which the ore itself will largely or most-ly supply the essentials, ifthese essentials are properly manipulated.

The process will novi7 be described somewhat in detail, reference beingmade to the accompanying drawing which is a flow sheet in diagrammaticplan of the process.

In describing the process, the ore to be treated may be presumed to be asulphide, or

a sulphide containing oxides which is commonly known as a mixed ore. Theore as it comes from the mine is ground to the desired fineness andconcentrated. The concentration may be done either by gravity orflotation or by both gravity and flotation combined. The sulphides areseparated from the gangue which may or may not contain sufficient oxideor carbonate of copper to Warrant further treatment.

The copper sulphide concentrate is divided into a high grade and a lowgrade concentrate, and given somewhat separate, although related,treatment. In the concentration treatment of copper ore, either' bygravity or flotation or both combined, a certain amount of very highgrade concentrate may be separated from the large amount of ordinarysulphide concentrate or from the ore, but the relatively small amount ofhigh grade concentrate will contain a relatively large amount of thetotal copper. Usually this relatively small portion of high' gradeconcentrate will be in the form of Chalcocite, with probably relativelysmall amounts of bornite and chalcopyrite, which will contaminate thehigh grade concentrate with a small amount of iron, but not enough toeffect the present process.

The copper in what is known as porphyry or disseminated deposits islargely in the form of chalcocite, CugS, and contains, theoretically,79.8% copper and 20.2% sulphur.

The conditions of concentration can best be illustrated by taking aspecificy case in the treatment of tons of ore assaying 1.5%, or 30pounds of copper per t0n, or containing a total of 3000 pounds ofcopper.

lf the ratio of concentration is 10 into '1,

the result of Lthe concentration treatment would be about as follows:

10 tons concentrate, 12.75% copper (25.5 lbs.) 2,550 lbs. total;

90 tons tailing, 0.25% copper (51 lbs.)

V150 lbs. total.

The ten tons of concentrate'may then be separated into:

1.5 tons high grade concentrate, 50% copper (1,000lbs), 1,500 lbs.total.

8.5 tons low grade concentrate, 6.2% copper (124i lbs), 1,050 lbs.total.

Or, possibly, into the following:

1.0 tons high grade concentrate, 60% cop,-V per 1,200 lbs.) 1,200 lbs.total.

9.0 tons low grade concentrate, 7.5% copper (150 lbs.) 1,350 lbs. total.

There should be no ditliculty in making a relatively small amount ofhigh grade concentrate, if much of the copper in the ore is in the formof chalcocite. For a 50%copper concentrate there would be margin of29.8% of the theoretical andV fora 60% copper concentrate there would bea margin of 10.0% of the theoretical. The latter is preferred and willbe assumed for illustration,

L cious metals in about the same proportion as it contains the copperfrom the original ore. That is to say, of the total precious metalcontent in the concentrate, 47.5% will be in the one ton of 60% copperconcentrate, and 52.5% will be in the 9.0 tons of lovv grade concentrateassaying 7.5% copper.

' Having made the separation of the mineral from the gangue and dividedthe minleral into a relatively small amount of high 5 grade concentrateand a relatively large amount of loiv grade concentrate, the method ofprocedure is as follows:

The low grade concentrate is roasted so as to convert a large part ofthe copper into the formfof sulphate, which is soluble in Water, andthis sulphate, on electrolysis, supplies the necessary acid for theprocess.

The roasted lovv grade concentrate is leached With a dilute acidsolution to extract the copper. The resulting copper solution,containing salts of iron, is then electrolyzed to deposit the copper,While at the same time acid and ferric iron are regenerated. Ferrie ironin the electrolyte is harinful. It redissolves copper from the cathodeapproximately proportional to its presence in the electrolyte. When theferrie ironin the electrolyte reaches 0.5% the. deposition of the copperbecomes ineflicient, and when it reaches 0.75% to 1.0% the processpractically becomes prohibitive. For good Work the solution flowing intothe copper deposit ing tanks should be as lovv in ferrie iron aspossible, and the solution issuing from the copper depositing tanksshould not greatly exceed 0.25% ferrie iron for good Work. It mayadvantageously be less. For the purpose of this process the ferric ironproduced by the deposition of the copper from the leach solutioncontaining salts of iron, is reduced with the high grade sulphideconcentrate, consisting largely of Cu2S and CuS. The reactions involvingthe reduction of the ferrie iron and the solution of the copper havebeen given in equation form.

By treating the copper solutionwobtained from the roasted lovv grade oreor concen-l trate, containing ferrie iron due to the electrolyticdeposition of the'copper, with the raw or unroasted high grade sulphideconcentrate, there Will result several distinct advantages, among Whichare: first, the reduction of the harmful ferric iron to the harmless orybeneficial ferrous iron which makes practical high depositionefficiency; second, the copper of the high grade unroasted concentrategoes into solution simultaneously with the reduction of the ferrie ironand is directly converted into the electrolytic metal; third, theexpense of drying and roasting the high grade concentrate, With itsattendant losses, is largely if not entirely avoided, and fourth, thesevarious factors combined result in an effectively and cheaply operatingprocess. Copper sulphide in a finely divided condition is an effectivereducing agent for ferrie iron, and probably its most effective form asa reducing agent is in the form of a Cu2S or CuS precipitate, as setforth in some detail in my patents No. 1,365,034, Jan. ii, i921; No.1,357,495, Nov. 2, 1920; and No. 1,489,121, Apr. 17 1924. A distinctadvantage however is gained by separating the high grade concentratefrom the low grade. concentrate and treating the leach solution andelectrolyte obtained from leaching the roasted low grade concentrateWith the unroasted high grade concentrate as set forth in this process,although substantially the same chemical reactions are involved.

It is preferred to electrolyze the copper solution obtained fromleaching the roasted low grade concentrate in steps, or in a. series ofelectrolytic units. If, for example, the rich copper solution from theroasted low grade concentrate contains 4.5% copper and it is desired toin'ipoverish it down to 2.0% copper before returning the solution to theroasted concentrate, it is preferred to do it in three electrolyticunits, each comprising a CugS or CnS reducer and an electrolyzer, orcopper tank, by taking out 1.0% of the copper in the first electrolyticunit and 0.7 in each of the remaining two. rlhe copper in the firstelectrolytic unit would be deposited out of an approximately 3.5% coppersolution; the copper in the second electro- Vlytic unit would bedeposited out of an approximately 2.75% copper solution, and the copperin the third electrolytic unit would.

the head solution is very high inl copper, three or more 'electrolyticunits, composing the series, may be desirable.

Ifthe copper deposited produced the theoretical equivalent or ferrieiron, then the ferrie iron so produced Would re-dissolve the sameequivalent or copper from the raw` high grade concentrate, but thetheoretical equivalent is never realized, and hence the copper depositedis obtained both from the roasted loW grade concentrate and from theu'nroasted high grade concentrate. The relative amounts'ivill largely bedependent on the de= tails or operation.

VSome of the oxygen' released at the anode Will be converted into acid,and when the solution becomes excessively charged with acid, the excessacid Will have to be neutralized, or a port-ion or the solution Wastedand an equivalent of Water added, or the excess acid maybe used inleaching oxidized ore, which in most instances Will be the tailings fromthe preliminary concentra-tion process for obtaining the high grade andthe low grade concentrate.

Both the acid and the iron in the solution can be largely controlled bythe method ot' roasting thel low grade concentrate. It acid is desiredthe roasting Would be conducted to convert as much as possible of thecopper into the sulphate, which, on electrolysis, Will render anequivalent of acidv and ferrie iron. It it is desired to suppress` theacid, the roastingA can be conducted so that most of the copper in theroasted low grade concentrate vvill loe in the form or oxide, which willrequire acid to bring the copper into solution. It iron is desired inthe solution or electrolyte, the roasting would be conducted underhighly sulphatizing conditions, which would give a high iron as Well asa high copper solubilityv in Water or dilute acid. If it is desired tosuppress the soluble iron the roasting should be highly `oxidizing. Inthis Way the process can loe largely regulated to conform With therelative amounts of high grade and low grade copper concentrateresulting from the prelimn inary treatment of the ore.. The processWorks best if the high grade concentrate is largely confined tochalcocite, Gu2S, and covellite, CUS. Chalcopyr'ite and hornite, orcopper bearing pyrites are not as eective in reducing fer-ric iron asthechalcocite or covellite. While there. Will inevitably loe some mixingof these copper minerals in the gravity or liotati'on concentration, theobject would naturally be to'have the 4high grade concentrate composedmostly or chalcocite and covellite With'a small `amount of v practicallypure chalcopyrite and bornite.

The low grade concentrate would be 'cornposed or what is lett.

1t is preferred to apply the high grade copper sulphide concentrate tothe electrolyte in a finely divided condition, in aseries of CnSreducers forming part 01"' the electrolytic units. Each CnS reducer mayconveniently consist of an agitator, a separator or settling tank, and apump to return settled lines from the settler to the agitator. Freshconcentrate may be used in all or the CnS reduce-rs, but it is preferredto put all or most of the fresh high grade raw concentrate in the tirstGuS reducer, or CnS reducer No. 1,- and then as the sulphide concentratebecomes impoverished in copper, pass it progressively from the GuSVreducer oi' the lir'st electrolytic unit to theV last, and tinally, whenthe high grade concentrate has been suiiiciently impoverished in copper,the `residue is added to the low grade 'concentrate and roasted with itto extract the remaining copper by leaching. The application ofconcentrated copper sulphide, obtained either as aprecipitate, aschalcocite from ore, or as obtained by fusion, as a reducing agent forterric iron produced by the electrolysis or copper solutions and thesubsequent roasting .and leaching of the copper sulphide residue, is set'forth in some detail in my patents No. 1,340,826, May ia, i920, No.1,357,495,N0v. a, i920; No. 1,489 ,121v April 1, 1924; No. 1,528,207,March 1925, and in my pending application, Serial No. 60,577, October5,- 1925. The present process, in this respect, is a modification orimprovement to accomplish the specific purposes set VVforth, and may heconsidered as a division of lmy pending application Serial No. 101,194,April 10, 1926.

Various' methods may be used in applying the high grade copperconcentrate to the electrolyzed solution to reduce the ferrie iron, butthe preferred method is to finely grind'the high grade concentrate andthen applyy it to the solution in an agitator, either or' the rotary orPachuca type, and letting the partly quiescent over-flow from theagitator How into the separator or settlerrto clarify the solution. Theclariiied solution from the settler Hows into the copper tanks orelectrolyzers, and the settled slime underioo s ica llU

iiow is returned to the agitator. A. portion v of the electrolyzedsolution. from one electrolytic unit is returned to vthe agitator of thesaine unit, While another portion-the advance flow-is advanced -to theagitator or the next electrolytic unit.y In this Way Y the solution andthe high grade concentrate are advanced through t-he series ofelectrolytic units. The solution issuing from the last electrolyzer orcopper 4depositing tank is returned to the roasted concentrate, and theresidue from the high grade concentrate :is added to the low gradeconcentrate to be roasted with it. V

rlhe reducing action `or the high ygrade rconcentrate is somewhatdependent, or inluenced by the temperature of Vthe solution.

The hot roasted ore, as also the electrolysis, Will tend to maintain thesolution fairly Warm, but in addition to this it may be desirable tomaintain the temperature of the solution above that due to the chemicalreactions and the hot ore by applying extraneous heat.

In operating the process, the ore as it comes from the mine is Separatedinto a relatively large amount of low grade concentrate and a relativelysmall amount of high grade sulphide concentrate.v lf the concentrationtailing is too lean to Warrant further treatment it is Wasted. If itstill contains values Worth recovering it is transferred to theconcentrate tailing leaching tanlr for the recovery of the remainingcopper.

rlhe low grade concentrate is roasted and then leached with a diluteacid solution, preferably with sulphuric acid, to extract the copper.lron goes into solution with the copper., and the amount of irondissolved Will depend mostly on the details of roasting.

The copper solution, containing salts of iron, iloivs into the agitatorNo. l or'settler No. l, and from there the clear overflow passes to theelectrolyzers, or copper tanks No. l, Where the copper is deposited andacid and ferrie iron are regenerated. rlChe flow of the solutionythrough the copper tanks is preferably at such a rate that the ferrieiron in the emuent solution will not greatly exceed 0.25%. The solutionisthen returned to the agitator and the cycle repeated. l/Vhen thesolution is agitated With the finely ground high grade copper sulphideconcentrate a certain amount of the concentrate slime Will pass With thesolution to the settler. A portion of this finely divided slime or highgrade concentrate is returned to the agitator by the pump No. l, and acertain amount, determined by experience and the results desired, isadvanced to the agitator of the next electrolytic unit, and so on to thethird, and finally, when the high grade sulphide copper concentrate isimpoverished in copper so that it is no longer effective as a reducingagent, it is deivatered or filtered and added to the low gradeconcentrate to be roasted With it. A portion of the copper from thecells of the first electrolytic unit is returned to the agitator, whileanother portion-the advance tion-is passed oir to the secondelectrolytic unit, and froml the second to the third or last unit, and`from the third or last unit it is returned to the roasted 10W gradeconcentrate Where it is again reduced in acid and enriched in copper,and the cycle repeated. rlhe amount of copper remaining in theelectrolyte in passing from one Y electrolytic unit to the next and thenumber of cycles Il each electrolytic unit, will depend on the amount ofcopper in the solution from the roasted low grade concentrate and theamount of copper dissolved from the raw or unroasted high gradeconcentrate, land the amount of acid in the solution. lt is notdesirable to have the solution excessively high in acid.

When the solution becomes too foul for effective use, either forleaching or electrolysis, la portion is diverted from the leaching andelectrolytic circuit and applied to the concentrator tailing or 10Wgrade oxidized ore to extract the copper therefrom. If the i resultingsolution is sufficiently pure and sufficiently high in copper, it may bereturned to the leaching and electrolytic circuit, With the excess acidpractically neutralized. If the solution is Very impure and 10W incopper, the solution, as also the Wash Water from leaching` both thelconcentrator tailing and the roasted low grade concentrate residue istreated to precipitate. the copper, and the copper precipitate may beapplied to the electrolyte the same as the high grade concentrate. It ispreferred to precipitate the copper from the lean and foul solutionsWith hydrogen sulphide, generated from iron sulphide and sulphuric acid,and using the resulting ferrous sulphate to regulate their'on content ofthel leaching and electrolytic solution circuit, should more iron bedesired in the solution than that furnished by the roasted low gradeconcentrate.

I claim:

l. A copper extraction process comprising, separating copper ore into ahigh grade and a low grade concentrate, roasting the lovv gradeconcentrate, leaching the roasted 10W grade concentrate With an acidsolution. to extract the copper, electrolyzing the resulting coppersolution containing salts of iron to deposit copper and regenerate acidand ferrie iron, applying the unroasted high grade sulphide concentrateto the electrolyzed solution to reduce the ferrie iron formed by theelectrolysis to the ferrous condition, and then again electrolyzing thesolution to deposit more copper.

2. A coppe-r extract-ion process comprising, separating copper ore intoa relatively small amount of high grade sulphide concentrate and arelatively large amount of low grade concentrate, roasting the low gradeconcentrate, leaching theroasted low grade concentrate with an acidsolution to extract the copper, electrolyzing the resultn ing coppersolution containing salts of iron to deposit copper and regenerateacidand ferrie iron, applying the unroasted sulphide concentrate to theelectrolyzed solution to reduce the ferrie iron formed by theelectrolysis to the ferrous condition and to dissolve copper from theunroasted high grade concentrate, andfthen again electrolyzing thesolution to deposit the copper dissolved from the roasted loW gradeconcentrate and from the unroasted high grade concentrate as theelectrolytic ineta 3. A copper extraction process comprising, treatingcopper ore to obtain a high vgrade and a loW grade copper concentrate,roasting the low grade concentrate, leaching the roasted low gradeconcentrate with an acid solution to extract the copper, then,alternately subjecting the resulting copper solution containing saltsoil iron to electroly- ,sis and tothe action Aolt the high grade sulironby alternately subjecting the solution" to electrolysis and to thereducing action of the unroasted `high grade concentrate, and when thesolution is impoverished in copper returning` the solution to `theroasted *low grade concentrate. y

5. A copper extraction process comprising, separating copper ore into Dahigh grade `and a low grade concentrate, roasting the low gradeconcentrate, leaching the roasted loiv grade concentrate with an acidsolution to extract the copper, electrolyzing the resulting coppersolution to deposit copper and regenerate acid and rferrie iron in aseries of electrolytic units each comprising an electrolyzcr and areducer, progressively advancing the solution from one electrolytic unitto the next oit Lthe series, and applying the :l'iigh grade. concentrateto the reducer (rt the lirst'electrolytic unit and progresisiveilyadvancing it through the reducers of `the series ott units.

6. A copper extraction 'process -coinprising, separating copper ore intoa high grade sulphide vconcentiate and a low grade con- Vcentrate,roasting the low grade concentrate, leaching the roasted'lniv gradeconcentratel to 'extract the copper., electrolyzing the resulting coppersolution containing'.

,salts of iron to deposit copper and regenerate 4acid and terric iron,appl-ying the unroasted sulphide concentrate vto :the electrolyzedsolution, generating hydrogen sulphide troni acid and ferrous, sulphide.precipitating copperhtroin the lean-and foul solutions with the"hydrogen sulphide, and adding .the resulting ferrous salt to the leachsolution and electrolyte.

f7. YAAcopper vext rac tion `.process compristhe copper and regenerateacid and ferrie iron in al series oi' electrolytic units each comprisingan electrolyzer anda reducer, circulating a portion of the solution be'tween the electrolyzer and the reducer of each oit the electrolyticunits, progressively advancing another portion of the solution troni oneelectrolytic unit to the next, and il applying the -liigh grade sulphideconcentrate to the solution in the reducers of the respectiveelectrolytic units. Y

8. A copper 4extraction process comprising, `treating copper ore toproduce a 'high grade copper sulphide `concentra-te and a lon7 gradeconcentrate, roasting the lovv grade concentrate, leaching the roastedlow grade concentrate with an-'acid solution to extract a portion of thecopper, electrolyzing the resulting copper solution containing salts ol'iron to deposit the copper and regenerate acid and ferrie iron in aseries of electrolytic units each comprising an electrolyzer and areducer, circulating a portion of the solution between the electrolyzerand the reducer ofeach ofthe electrolytic units, progressively advancinganother portion of thesolution from one electrolytic unit to the next:of the series, applying the high grade copper sulphide concentrate tothe solution in the reducers oft the respective -electrolytic units, andwhen the solution becomes impoverished in copper returning the solutionto the roasted lovv grade concentrate and repeating the cycle.

9. A copper extraction process comprising, treating copper ore toproduce a high grade sulphide copper concentrate and a low gradeconcentrate, roasting the flovv grade concentrate, leaching the vroastedlow grade concentrate with an acid solution to extract the Til copper,electrolyzingfthe resultingcopper so- Y vlution containing salts'of ironto deposit the copper and regenerate acid and ferrie iron in a scrics otelectrolytic units each comprising au electrolyzer and a reducer,circulating a portion ot' the solution between the electro- `l-yZer andthe reducer of each of the electro-- ;ingtreating cepper cre Ate"produce a high grade copper sulphide concentrate and a low gradeconcentrate, roasting the low grade concentrate,leaching the roasted lowgrade concentrate With an acid solution to extract a portion ot thecopper, electrolyzing the resulting copper solutioncontaining salts ofiron to deposit the copper and regenerate acid and ferric iron in aseries of electrolytic units each comprising an electrolyzer and areducer, circulating a portion of the solution between the electrolyzerand the reducer of each of the electrolytic units, progressivelyadvancing another portion of the solution from one electrolytic unit tothe next of the series, applying the high grade copper sulphideconcentrate to the solution in the reducers of the respectiveelectrolytic units, and when the solution becomes impoverished in copperreturning' the solution to the roasted low grade concentrate to extractanother portion ot the copper therefrom and repeating the cycle, andwhen the high grade copper sulphide concentrate becomes impoverished incopper mixing the residue with the unroasted loW grade concentrate,roasting` the mixture, and leaching the roasted mixture With theimpoverished electrolyzed copper solution.

11. A copper extraction process compris ing, treating copper ore toproduce a high grade copper sulphide concentrate and a lovv gradeconcentrate, roasting the low grade concentrate with an acid solution toextract the copper, electrolyzing the resulting copper solutioncontaining salts of iron to deposit the copper and regenerate acid andt'erric iron, applying the unroasted sulphide concentrate to theelectrolyzed solution in a reducer consistingof an agitator and asettler to reduce the ferrie iron :termed by the electrolysis to theferrous condition, circulating the solution between the electrolyzer andthe agitator and the settler .and back to the electrolyzer, andreturning settled solids from the settler to the agitator.

l2. A copper extraction process comprising, treating copper ore toobtain a high grade sulphide copper concentrate and a lovv grade copperconcentrate, roasting the low grade concentrate, leaching the roastedloW grade concentrate with an acid solution to extract the copper, thenalternately subjecting the resulting copper solution containing saltsot' iron to electrolysis and to the action or' the high grade sulphideconcentrate to obtain the copper of both the high grade unroastedconcentrate and the copper of the roasted low grade concentrate as theelectrolytic metal, and maintaining the solution at a temperature abovethat due to chemical reactions of the process.

WILLIAM E. GREENAVALT.

liti

